17 



pired air thus : "It will follow that in the precipitation of lime by breath- 

 ing into lime water the fixed air which incorporates with lime comes not 

 from the lungs but from the common air, decomposed by the phlogiston 

 exhaled from them." And Priestley, who was one of the discoverers of 

 oxygen, was gathered to his fathers at Northumberland, Pennsylvania, in 

 1804, still believing the phlogiston theory of combustion. 



Crawford (1748-1795) was the first individual to publish experiments 

 on animal calorimetry. In 1777 he found, after burning wax and carbon 

 or on leaving a live guinea-pig in his water calorimeter, that for every 

 100 oz. of oxygen used the water was raised the following number of 

 degrees Fahrenheit: 



Wax 2.1 



Carbon 1.93 



Guinea-pig 1.73 



Crawford states, "Animal heat seems to depend upon a process similar 

 to a chemical elective attraction." However, the theory of phlogiston 

 renders Crawford's work quite unintelligible and in the second edition 

 of his "Experiments and Observations Animal Heat," published in 1788, 

 one still finds statements like this, "Now it has been proved that when 

 an animal is surrounded by a medium at a low temperature it phlogisti- 

 cates a greater quantity of air in a given time than when it is surrounded 

 by a warm medium." 



Scheele (1742-1786). Independent of Priestley and before him, 

 Scheele, a Swedish apothecary and eminent chemist, discovered oxygen 

 by decomposing dioxid of manganese and other substances. Scheele be- 

 lieved that the atmosphere was composed of "spoiled air" and "fire air." 

 When a body burned in air it lost its phlogiston, which united with "fire 

 air." Heat consisted of "fire air" united with phlogiston. It passed 

 through glass. In this way a portion of air could pass through glass, 



In 1771 Scheele (Scheele, 1793) had found that when silver carbonate 

 was heated in a retort "fixed air" was liberated as well as "fire air," 

 while a residue of metallic silver remained. In 1775 he placed silver 

 carbonate in a small retort connected with a collapsed bladder and then 

 heated the substance. Two airs were evolved, "fixed air" which he re- 

 moved with lime water, and "fire air" in which a flame burned brightly. 

 In the interim between these two experiments he wrote Lavoisier in 

 Paris a letter dated September 30, 1774, asking him to use his powerful 

 burning glass upon silver carbonate, then to absorb the "fixed air" in 

 lime water and observe whether a candle would burn and an animal live 

 in the remaining air, and he begged Lavoisier to inform him of the 

 results. 



Scheele performed another striking experiment (Scheele, 1777). He 

 placed two large bees together with a little honey in a small upper chamber 



